1hz completely broken flex plate. What would cause this? (1 Viewer)

[craigbuilt]

So I have a 1hz with a a442f auto tranny. I am running a whole sale automatic torque converter. I have put roughly 2500 miless on it since this failure appeared. The flex plate cracked in a complete circle around the crank bolts. The noise that it made was NOT GOOD. It sounded like a bottom end knock. It wasn't until after I pulled the pan, BEBs, head ect and found nothing that I stumbled across metal pieces falling out of the bell housing inspection cover. Yippiee....

Anyway has anyone seen this before? What would cause this failure?

Thanks

 

[lostmarbles]

Too much misalignment?

AGCO Automotive Repair Service - Baton Rouge, LA - Detailed Auto Topics - What Causes A Flexplate To Crack

 

[craigbuilt]

Thank you.
I have been doing some digging as well. I'm going to replace the end plate. Have the torque converter checked for balance. New flexplate obviously, Check the dowel pins. Check crankshaft runout. Replace crank bolts. add back the spacer/ crank bolt washer.

As you can see in the photo the washer was not present and the bolts had to be machined down to clear the previous torque converter, per spec. Current converter will clear with spacer and standard bolts. .

By doing all the above I hope I don't have this problem again. If there is something else I should do or check please chime in.

Thanks

 

[dousty]

You mean this thing? It will support's the area of the flex plate that has cracked out.

 

[lostmarbles]

You mean this thing? It will support's the area of the flex plate that has cracked out. View attachment 1207307

I have niltch in the way of experience in these plates but I'd guess if this plate was left out when it was supposed to be there then it is likely to be the main cause of the failure.

It looks to me like it is not just a "spacer" but is designed to prevent the plate from flexing in the weak bolt-circle-area where it has cracked up.

 

[craigbuilt]

Yes, the plate was intentionally left out and the crank shaft bolts were ground down to 1/4 inch left on the head Per the manufacturer instructions. Required in order for the new torque converter to fit. Although I don't believe that removing the washer and grinding down the bolts would help in any way. It may not have caused the failure.

I had the torque converter checked for balance. And it was a little out, but still with in spec.

I think I located the cause of the failure. Upon a close inspection I noticed one of the dowel pins in the bell housing was missing. In removing and reinstalling the Trans over 5 times, over the past 8 months.... ( very long story)... it must have fallen out with out me noticing. So a $1.68 part potential cost me lots of $$$$$. Dang it.